Hey there - thanks for your question! Whether or not to mute the strings that are ringing out through the amp is a personal choice. You might not mind that sound if you're playing a loud rock song, but maybe, if you're playing a technical passage, you'd want it to sound as clean as possible. It is a great skill to learn how to mute the strings so that you can do it when you desire. I recommend checking out this tutorial:

https://www.guitartricks.com/tutorial/2281

Hope this helps!